In recent years, in order to allow a semiconductor device such as a metal oxide semiconductor field effect transistor (MOSFET) to be high in breakdown voltage and low in loss and to be used in a high-temperature environment, silicon carbide has been increasingly adopted as a material forming a semiconductor device. Silicon carbide is a wide band gap semiconductor having a band gap larger than that of silicon, which has been conventionally widely used as a material forming a semiconductor device. Hence, by adopting silicon carbide as a material forming a semiconductor device, the semiconductor device can have a high breakdown voltage, reduced on-resistance, and the like. Further, the semiconductor device thus adopting silicon carbide as its material has characteristics less deteriorated even under a high temperature environment than those of a semiconductor device adopting silicon as its material, advantageously.
For example, “Performance of 60 A, 1200V 4H—SiC DMOSFETs”, by Brett A. Hull et al., Materials Science Forum, Vols. 615 to 617, 2009, pp. 749 to 752 (NPD 1) discloses a MOSFET having an n type drift layer formed on a silicon carbide substrate, a pair of well regions, and a gate insulating film. The above document discloses a MOSFET having a switching energy loss of 9 mJ when it is switched from an ON state in which a drain source current is 65 A to an OFF state in which a drain source voltage is 750 V.